Connections of the parabrachial nucleus with the nucleus of the solitary tract and the medullary reticular formation in the rat

Abstract

We examined the subnuclear organization of projections to the parabrachial nucleus (PB) from the nucleus of the solitary tract (NTS), area postrema, and medullary reticular formation in the rat by using the anterograde and retrograde transport of wheat germ agglutinin-horseradish peroxidase conjugate and anterograde tracing with Phaseolus vulgaris-leucoagglutinin. Different functional regions of the NTS/area postrema complex and medullary reticular formation were found to innervate largely nonoverlapping zones in the PB. The general visceral part of the NTS, including the medial, parvicellular, intermediate, and commissural NTS subnuclei and the core of the area postrema, projects to restricted terminal zones in the inner portion of the external lateral PB, the central and dorsal lateral PB subnuclei, and the "waist" area. The dorsomedial NTS subnucleus and the rim of the area postrema specifically innervate the outer portion of the external lateral PB subnucleus. In addition, the medial NTS innervates the caudal lateral part of the external medial PB subnucleus. The respiratory part of the NTS, comprising the ventrolateral, intermediate, and caudal commissural subnuclei, is reciprocally connected with the Kölliker-Fuse nucleus, and with the far lateral parts of the dorsal and central lateral PB subnuclei. There is also a patchy projection to the caudal lateral part of the external medial PB subnucleus from the ventrolateral NTS. The rostral, gustatory part of the NTS projects mainly to the caudal medial parts of the PB complex, including the "waist" area, as well as more rostrally to parts of the medial, external medial, ventral, and central lateral PB subnuclei. The connections of different portions of the medullary reticular formation with the PB complex reflect the same patterns of organization, but are reciprocal. The periambiguus region is reciprocally connected with the same PB subnuclei as the ventrolateral NTS; the rostral ventrolateral reticular nucleus with the same PB subnuclei as both the ventrolateral (respiratory) and medial (general visceral) NTS; and the parvicellular reticular area, adjacent to the rostral NTS, with parts of the central and ventral lateral and the medial PB subnuclei that also receive rostral (gustatory) NTS input. In addition, the rostral ventrolateral reticular nucleus and the parvicellular reticular formation have more extensive connections with parts of the rostral PB and the subjacent reticular formation that receive little if any NTS input. The PB contains a series of topographically complex terminal domains reflecting the functional organization of its afferent sources in the NTS and medullary reticular formation.

A bilateral cortico-bulbar network associated with breath holding in humans, determined by functional magnetic resonance imaging

“…The precise role of pontine neurons in respiratory modulation remains unclear since stimulation of different regions of the dorsolateral pons can result in tachypnea, bradypnea, apneusis or apnoea (Chamberlin and Saper, 1994;Fung and St John, 1994;Mutolo et al, 1998). Neurones within the dorsolateral pons have reciprocal connections, some via the ventrolateral pons (Herbert et al, 1990;Song and Poon, 2004), with respiratory neurones within the ventrolateral medulla (Ellenberger and Feldman, 1990;Herbert et al, 1990;Song and Poon, 2004), and some of these neurones project to the nucleus tractus solitarius (Herbert et al, 1990) and phrenic motoneurones (Yokota et al, 2001). Evidence for whether respiratory rhythmic output persists during breath holding is unclear.…”

“…Vagal fibres transmitting afferent information from the lungs, chest wall and respiratory muscles as a result of lung inflation, project to and terminate onto neurones within the nucleus of the solitary tract (Bianchi et al, 1995), which in turn project to the parabrachial nucleus (Cechetto, 1995;Herbert et al, 1990). Although it is possible that the pontine activity identified in this study reflects sensory feedback from the lungs, we think this is unlikely because the protocol was designed to minimise afferent signalling by performing the breath hold at resting expiratory lung volume (i.e.…”

Ascending Projections from the Area Postrema and the Nucleus of the Solitary Tract of Suncus Murinus

“…It was suggested later that the major neural target of the AP might be a specific region within the LPb, the external subdivision (van der Kooy and Koda, 1983; Cunningham et aL, 1994). Herbert et al (1990) used an anterogarde tracing technique to examine the subnuclear organization of the AP-Pb projection in the rat. According to their findings, the core of the AP projected to the central, external, and dorsal subdivisions of the LPb.…”

“…Based on physiological studies, the AP has generally been recognized to act as a "chemoreceptor trigger zone" for the induction of emesis (Borison et al, 1984;Carpenter, 1989), however, there have been few morphological studies concerning the neuronal mechanisms which underlie the emetic reflex via the AP. Some studies have reported on the nature of the connectivity of the AP, but most have used the rat as their model, which, unlike the suncus, is not prone to vomiting (van der Kooy and Koda, 1983; Shapiro and Miselis, 1985a;Herbert et aL, 1990;Cunningham et aL, 1994). In the ferret, a species with a high incidence of vomiting, Strominger et aL (1994) demonstrated that the AP has reciprocal connections only with the nucleus of the solitary tract (NTS), which is generally accepted as the primary recipient of gustatory, cardiovascular, pulmonary, and gastrointestinal sensory afferents.…”

Lesions of the commissural subnucleus of the nucleus of the solitary tract increase isoproterenol-induced water intake

“…The medial NTS (mNTS) and the commissural NTS (commNTS) subnuclei project to the forebrain areas involved in the control of hydroelectrolyte balance, such as the paraventricular nucleus and the anteroventral third ventricle region and to hindbrain areas such as the LPBN (14)(15)(16) and receive projections from the AP (17). Besides playing a well-established role in cardiovascular regulation (18)(19)(20), the NTS may also be involved in the control of fluid balance.…”